Modular radial head prosthesis

ABSTRACT

A method for implanting a prosthesis system for replacement of a head portion of a proximal radius includes determining a distance between a proximal radius and a humerus. The method also includes selecting one of a first head component or a second head component based on the determination. The first and second head components have unique heights. The method further includes connecting the selected first or second head component to an articulation component and connecting a stem component to the selected first or second head component.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.12/794,196, filed Jun. 4, 2010, which is a continuation-in-part of U.S.patent application Ser. No. 12/578,052, filed Oct. 13, 2009 (now issuedas U.S. Pat. No. 8,425,615 on Apr. 23, 2013), which is a continuation ofU.S. patent application Ser. No. 10/999,297, filed Nov. 29, 2004 (nowissued as U.S. Pat. No. 8,114,163 on Feb. 14, 2012), which is acontinuation-in-part of U.S. patent application Ser. No. 10/464,043,filed on Jun. 18, 2003 (now abandoned), which is a continuation of U.S.patent application Ser. No. 09/828,745, filed Apr. 9, 2001 (now issuedas U.S. Pat. No. 6,656,225 on Dec. 2, 2003), which claims the benefit ofU.S. Provisional Application 60/195,444, filed Apr. 10, 2000. Thedisclosures of the above applications and patents are herebyincorporated by reference as fully set forth herein.

FIELD

The present disclosure relates to a humeral implant and morespecifically relates to a method and apparatus for adjusting the heightand/or the angle of the humeral implant.

BACKGROUND

Trauma to the elbow joint frequently involves damage to the ligamentoussupport of the elbow and fractures of the osseous structures responsiblefor the skeletal integrity of the elbow joint. The proximal aspect ofthe radius, or radial head, is frequently injured either in isolation orin combination with injury to other bony or ligamentous structures ofthe elbow joint. The radial head may also be fractured in associationwith injuries to the forearm axis, including disruptions of theinterosseous membrane between the radius and the ulna. Whether inisolation or in combination with other injuries, fractures of the radialhead can be difficult to treat.

Fractures of the radial head are either reconstructable orunreconstructable. Despite various technical advances in thereconstruction of radial head fractures, a certain percentage offractures are not amenable to reconstruction due to the degree ofcomminution or severity of the fracture. In general, unreconstructableradial head fractures result from high energy trauma and are thereforefrequently associated with significant injuries to other osseous orligamentous structures of the elbow joint or forearm. In these cases,restoration of the stabilizing function of the radial head is criticalto allow the ligaments of the elbow or forearm to heal in appropriaterelationships, thereby restoring stability to the elbow or forearm. Thisstabilizing function depends, in part, upon re-establishing theappropriate distance between the capitellum and the proximal shaft ofthe radius.

Prosthetic replacement of the radial head has evolved rather slowly. Thefirst widely used prosthetic radial head was introduced in the 1970'sand was composed of silicone. Silicone implants placed in various jointsthroughout the body led to “silicone synovitis,” in which the siliconeinduced an inflammatory response within the joint. Further, siliconeradial head prostheses were found to be incapable of resisting thestresses to which the radial head is subjected, rendering it less usefulin stabilizing the injured elbow or forearm.

The difficulties apparent with silicone led to experimentation withmetal radial head implants. These prostheses are fashioned from a singlepiece of metal (often titanium) and include a stem and a head portion.The head portion is shaped to approximate the anatomy of the radialhead. These metallic prostheses are capable of resisting the compressivestresses to which the radial head is subjected, as has been demonstratedin several biomechanical studies. However, significant problems remainwith these prostheses.

Anatomic and radiographic studies of the dimensions of the radial headreveal a disparity with currently available metallic prostheses.Therefore it has been difficult to restore appropriate anatomicalignments within the elbow. Therefore restoration of the appropriaterelationship between the capitellum and proximal shaft of the radius hasbeen very difficult to achieve with these prostheses. Additionally, thefact that these prostheses are fashioned from a single piece of metalhas led to technical difficulties with insertion and removal. Surgeonshave had difficulty with matching both the size of the stem to the canalof the proximal radius and the size of the head portion to the patient'snative radial head. Removal of these non-modular components frequentlyrequires release of the lateral ligaments of the elbow and the annularligament, which binds the neck of the proximal radius to the proximalulna. Thus the elbow is frequently destabilized during removal of theseprostheses.

Designers of prosthetic joint replacements in the hip, shoulder, kneeand fingers have circumvented the above mentioned difficulties byemploying the use of modular components. Modularity allows for eachaspect of a prosthesis to be sized appropriately to its recipientanatomic site. The concept of modularity has only recently been appliedto commercially available radial head prostheses. Currently availablemodular radial head prostheses employ a mechanism by which the headcomponent is impacted over and onto the stem component. The surgicalexposure must therefore allow sufficient room for the head to bemaneuvered over the stem prior to being impacted. With impaction, theheight of the prosthesis may be decreased, resulting in an increaseddistance between the capitellum and the proximal end of the radius.Increasing this distance alters the bony anatomy such that the ligamentsof the elbow joint are not held in their appropriate lengths andtensions. Instability of the elbow or inappropriate healing of theligaments may result. Furthermore, removal of these prostheses isaccomplished in the same manner as the above mentioned metallicimplants, often requiring destabilization of the lateral aspect of theelbow joint.

In order to reap the benefits of modularity in radial head prostheticreplacement, a reliable and surgically appropriate method to secure thestem of the prosthesis to the head of the prosthesis and which allowsfor accurate restoration of the appropriate spatial relationshipsbetween the bones of the elbow is required.

SUMMARY

In accordance with one aspect of the present disclosure, a method forimplanting a prosthesis system for replacement of a head portion of aproximal radius is provided. The method can include determining adistance between a proximal radius and a humerus. The method can alsoinclude selecting one of a first head component or a second headcomponent based on the determination. The first and second headcomponents can have unique heights. The method can further includeconnecting the selected first or second head component to anarticulation component and connecting a stem component to the selectedfirst or second head component.

In accordance with another aspect of the present disclosure, a methodfor implanting a prosthesis system for replacement of a head portion ofa proximal radius is provided. The method can include determining adistance between a proximal radius and a humerus. The method can alsoinclude selecting an articulation component and a head component basedon the determination. The articulation component can have a firstconnection portion. The head component can have a second connectionportion. The method can further include reducing a dimension of one ofthe articulation component or the head component from a first size to asecond size. The method can also include advancing one of thearticulation component or the head component into contact with the otherof the articulation component or head component and returning thedimension to the first size such that the first and second connectionportions interlock.

Further areas of applicability of the present disclosure will becomeapparent from the detailed description provided hereinafter. It shouldbe understood that the detailed description and specific examples, whileindicating the preferred embodiment of the disclosure, are intended forpurposes of illustration only and are not intended to limit the scope ofthe disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure will become more fully understood from thedetailed description and the accompanying drawings, wherein:

FIG. 1 is a front view of a stem component;

FIG. 2 is a side view of the stem component from a perspectiveperpendicular to that of FIG. 1;

FIG. 3 is a top view of the stem component;

FIG. 4 is a front view of an inner core of a head component;

FIG. 5 is a side view of the inner core of the head component from aperspective perpendicular to that of FIG. 4;

FIG. 6 is a top view of the inner core of the head component;

FIG. 7 is a front view of an outer shell of the head component;

FIG. 8 is a side view of an outer shell of a head component from aperspective perpendicular to that of FIG. 7;

FIG. 9 is an exploded perspective view of an assembly of a stemcomponent, an inner core, and an outer shell;

FIG. 10 is a perspective view of an assembled prosthesis;

FIG. 11 is a front view of an assembled prosthesis;

FIG. 12 is a side view of an assembled prosthesis from a perspectiveperpendicular to that of FIG. 11;

FIG. 13 is a top view of an assembled prosthesis;

FIG. 14 is a posterior oblique view of a human elbow depicting a radialhead prosthesis in position within a proximal radius bone andarticulating with a capitellum of a distal humerus;

FIGS. 15 and 16 are perspective views of a tool that can be used toinsert or remove a head component from a stem component via atranslational force;

FIG. 17 is a perspective view of the head component showing the outershell body completely enveloping the inner core;

FIG. 18 is similar to FIG. 17 but shows the head component disassembled;

FIG. 19A is a perspective view of the head component showing the innercore extending beneath the outer shell body;

FIG. 19B is similar to FIG. 19A but shows a mechanical fastener securingthe outer shell body to the inner core;

FIG. 19C is similar to FIG. 19A but shows the head components as asingle piece;

FIG. 20 is similar to FIG. 19 but shows the head component disassembled;

FIG. 21A is a perspective view of the head component, the stem componentand a collar component;

FIG. 21B is similar to FIG. 21A but shows an alternative configurationbetween the head component, the stem component and the collar component;

FIG. 22 is similar to FIG. 21A but the components are assembled;

FIG. 23 are perspective views of exemplary alternative connectionsbetween components of the modular prosthesis;

FIG. 24 is similar to FIG. 21A but shows an angled collar component;

FIG. 25 is similar to FIG. 24 but the components are assembled;

FIGS. 26A-26D are perspective views of exemplary alternative connectionsbetween the head component, the stem component and the collar component;

FIG. 27 is a perspective view of a kit including a plurality of headcomponents, stem components and collar components having various sizes,shapes and configurations;

FIG. 28 is a proximal perspective view of an articulation component andhead component of a modular radial head prosthesis system according toone example of the present teachings;

FIG. 29 is a distal perspective view of the articulation component andhead component of FIG. 28;

FIG. 30 is an exploded perspective view of the modular radial headprosthesis system of FIGS. 28 and 29 further illustrating a stemcomponent and a fastener;

FIG. 31 is an exploded cross-sectional view of the modular radial headprosthesis system illustrating a plurality of head components havingdifferent dimensions;

FIGS. 32 a and 32 b are partial cross-sectional views of thearticulation component and head component illustrating an exemplaryassembly sequence;

FIG. 33 is a cross-sectional view of the modular radial head prosthesistaken along lines 33-33 of FIG. 29;

FIGS. 34 and 35 are partial cross-sectional views of the modular radialhead prosthesis illustrating an exemplary assembly sequence attachingthe stem component;

FIG. 36 is an exploded perspective view of a modular radial headprosthesis system constructed in accordance to another example of thepresent teachings;

FIGS. 37 and 38 are cross-sectional views of the modular radial headprosthesis system of FIG. 36 illustrating an exemplary assemblysequence;

FIG. 39 is an exploded perspective view of a head prosthesis systemincluding an articulating component and a head component according toother features of the instant disclosure;

FIG. 40 illustrates a cross-sectional view of the head prosthesis systemtaken along lines 40-40 of FIG. 39;

FIG. 41 is a cross-sectional view of the head prosthesis system shownwith the articulating component being reduced in size from a firstposition (phantom line) to a second position (solid line) during anassembly step; and

FIG. 42 is a cross-sectional view of the head prosthesis system of FIG.41 and shown with the articulating component having a compression fitwith the head component once the articulating component returns to itsoriginal size.

DETAILED DESCRIPTION OF THE VARIOUS EMBODIMENTS

The following description of the preferred embodiment(s) is merelyexemplary in nature and is in no way intended to limit the disclosure,its application or uses.

Before the present disclosure is disclosed and described, it is to beunderstood that this disclosure is not limited to the particularconfigurations, process steps and materials disclosed herein as thesemay vary to some degree. It is also to be understood that theterminology used herein is used for the purpose of describing particularembodiments only, and is not intended to be limiting as the scope of thepresent disclosure. The disclosure will be limited only by the appendedclaims and equivalents thereof.

It must be noted that, as used in this specification and the appendedclaims, singular forms of “a,” “an,” and “the” include plural referentsunless the content clearly dictates otherwise.

“Radial head” is defined as the essentially cylindrical protrusion foundat the proximal end of a radius bone. The term “radial head” can also beused to modify or describe the prosthesis of the present disclosure.

“Longitudinal axis” is an imaginary line that is defined by the centerof the stem component in the direction of intramedullary canalinsertion. Thus, the “longitudinal axis” is also roughly defined asrunning parallel to a centerline running between the proximal and distalend of the radius bone.

“Transverse axis” or “assembly axis” is an axis that intersects thelongitudinal axis. The transverse axis can be linear or non-linear. Forexample, if non-linear, the axis can be arcuate, provided the assemblyaxis intersects the longitudinal axis. Thus, angles >0° and <180°qualify as “transverse.” However, for practical purposes, the transverseaxis can be from 45° to 135° with respect to the longitudinal axis inorder to significantly benefit from the modular assembly benefitsdescribed herein. In many instances, an essentially perpendiculartransverse axis with respect to the longitudinal axis will be present.

“Protuberance” can include any protuberance functional with the presentdisclosure, particularly with respect to certain locking mechanisms. Forexample, such protuberances can be convexities.

“Concavity” is intended to describe an open space defined by a mountingportion of a stem component, or an inner core. With respect to a lockingmechanism, the concavity can be configured to inversely match and accepta protuberance, though this is not required.

“Intramedullary” shall mean within the marrow cavity of a bone.

“Native” is used to describe the condition of the bone or the head of abone prior to damage or removal.

For the purposes of promoting an understanding of the principles of thedisclosure, reference will now be made to the exemplary embodimentsillustrated in the drawings, and specific language will be used todescribe the same. It will nevertheless be understood that no limitationof the scope of the disclosure is thereby intended. Any alterations andfurther modifications of the inventive features illustrated herein, andany additional applications of the principles of the disclosure asillustrated herein, which would occur to one skilled in the relevant artand having possession of this disclosure, are to be considered withinthe scope of the disclosure.

In order to remedy the shortcomings of prosthetic radial headreplacement, a radial head prosthesis is disclosed that enables theassembly without having to significantly remove or manipulate bone andtissue as part of an overhead assembly. By implementing a slidingmechanism for the assembly of the modular radial head prosthesis asdescribed herein, improvement over the commercially availableprosthetics can be achieved. Specifically, a sliding mechanism inconjunction with a locking mechanism enables the secure attachment andreasonable removal of a head component from an intact stem component,without the disadvantages associated with head component insertion alongthe longitudinal axis.

With the above descriptions and definitions in mind, a stem component 10is shown in FIG. 1. Generally, the stem component 10 comprises ananchoring portion 12 and a mounting portion 14. The anchoring portion 12is the portion that is anchored within a canal of the proximal radius,providing support to the radial head prosthetic as a whole. In thisembodiment, the anchoring portion 12 is tapered and can be coated ortextured to allow bone ingrowth after insertion into the radius bone ofa patient. The anchoring portion can be cemented, press fit, and/orimpacted into the intramedullary canal as is known by those skilled inthe art. If a cement is used, then a cement such as, for example, methylmethacrylate, can be used. If desired, various sized broaches (notshown) can be provided such that the surgeon can sound the diameter ofthe proximal radial shaft, thereby selecting an appropriate sized stemcomponent. In this embodiment, the mounting portion 14 is configured asa dovetail shaped mount when viewed from the front perspective shown inFIG. 1. On each side of the mounting portion 14 are the stemprotuberances 16 a, 16 b. Though not required, the entire stem component10 (i.e., the anchoring portion 12, the mounting portion 14, and thestem protuberances 16 a, 16 b) can be constructed of a rigid materialsuch as metal, alloy, or ceramic. If the rigid material is metal oralloy, appropriate materials can include, for example, titanium,stainless steel, and cobalt chrome.

Turning to FIG. 2, a side view of the stem component 10 is shown. As canbe seen, the stem protuberances 16 a are configured to span a distanceof approximately one half of the depth of the mounting portion. The stemprotuberance 16 b (not shown) is configured similarly. In FIG. 3, a topview of the stem component 10 is shown. As the mounting portion 14 isconfigured in a dovetail-type shape, the stem protuberances 16 a, 16 bare not visible from this perspective, and thus, are shown as dashedlines.

The stem component shown in FIGS. 1-3 has the dual purpose of attachingthe prosthesis to the radius bone, as well as to provide a mechanism tomount a head component (not shown) to the stem component. Though thehead component can be a single unit, in the embodiment shown in thesubsequent figures, the head component comprises an outer shell and aninner core. The practical reason for this is that it is often desirableto have a rigid outer shell, while having a less rigid inner core whenutilizing the locking mechanism described in FIGS. 1-13. However, if thelocking mechanism does not utilize compressible protuberances as part ofthe locking mechanism, the inner core can be a rigid material as well.FIGS. 3-6 show an embodiment of the inner core, and FIGS. 7-8 show anembodiment of the outer shell. However, the inner core and the outershell will generally be pre-assembled prior to surgery.

Turning specifically to FIG. 4, an inner core 20 of a head component isshown. An inner core body 22 defines the shape of the inner core 20 andcan be constructed of a polymeric resin, such as, for example, a highmolecular weight polyethylene. Additionally, the outer dimension of theinner core body 22 can be cylindrical in shape. Attached to the innercore body are a pair of inner core protuberances 24 a, 24 b. The innercore body 22 and the inner core protuberances 24 a, 24 b define an innercore open channel or groove 26 that can be slidably connected to themounting portion (not shown) of the stem component (not shown). Theinner core protuberances 24 a, 24 b can be constructed of the samematerial as the inner core body 22, though this is not required. Thus,the inner core body 22 and the inner core protuberances 24 a, 24 b canbe a single polymeric or copolymeric unit. Whatever the structure, inthis embodiment, the inner core protuberances 24 a, 24 b are constructedof a compressible material so that the inner core protuberances 24 a, 24b can pass by the stem protuberances (not shown) as part of a lockingmechanism.

As can be seen more clearly in FIGS. 5 and 6, the inner coreprotuberances 24 a, 24 b are configured such that they span only aportion of the depth of the open channel 26. Thus, the inner coreprotuberances 24 a, 24 b are positioned opposite the stem protuberances(not shown) such that when the head component is in place on the stemcomponent, all of the protuberances act together to form a lockingmechanism.

As shown in this embodiment, the inner core open channel 26 does nottraverse completely through the inner core body 22. Thus, the inner coregroove 26 is just long enough such that when the mounting portion of thestem component (not shown) is tracked within the inner core open channel26, the mounting portion and the inner core 20 will be coaxial.

In FIGS. 7 and 8, a radial head component 30 is shown. An outer shellbody 32 is fashioned to approximate the dimensions of a damaged orremoved radial head. Thus, the outer dimension is roughly cylindrical,having a slightly concaved top portion 37 for natural articulation withthe capitellum (not shown). Because outer shell body 32 is the portionof the prosthesis that will articulate with the capitellum upon jointmovement, this structure can be constructed of a biologically acceptablerigid material. Such a material can include, for example, metal, alloy,or ceramic. If the rigid material is metal or alloy, appropriatematerials can include, for example, titanium, stainless steel, andcobalt chrome. The outer shell body 32 also defines an inner hollow 34that accepts the inner core (not shown) when the head component is fullyconstructed. Additionally, an outer shell open channel or groove 36 ispresent that essentially matches the inner core open channel or groove(not shown) such that the mounting portion (not shown) can be insertedinto the aligned grooves. For example, the outer shell body 32 and theinner core (not shown) can both be cylindrical components that definedovetail shaped grooves, which substantially fits the dovetail shapedmount of the stem component. If the inner core 20 and the outer shellbody 32 are two different materials (as in the present embodiment), thenthe two components can be fitted together with a bonding cement,friction fit, and/or other known techniques. The outer shell openchannel or groove 36 can be present at only one edge of the outer shellbody 32 and its edges can be tapered to avoid damage to the articularcartilage of the proximal radial-ulnar joint. As mentioned, the outershell body 32 should be composed of metal suitable for biologicimplantation, and be shaped to approximate the dimensions of the radialhead. If the surgeon requires assistance in selecting an appropriatelysized head component, then an estimate of the patient's anatomy can beascertained using plastic trials (not shown) provided for this purpose.Though not required, the edges of the outer shell groove 36 can betapered to avoid damage to the proximal radial-ulnar joint.

Turning to FIG. 9, an exploded view of an embodiment of the presentdisclosure is shown. Specifically, the radial head component 30 is shownhaving an outer shell body 32, which defines an outer shell hollow 34.The outer shell hollow 34 fits over an outer dimension of the inner corebody 22 of the inner core 20. Once the outer shell body 32 and the innercore 20 are fitted together such that the outer shell open channel 36aligns with the inner core open channel 26, the entire head component(which comprises these two components) can be fitted on the mountingportion 14 of the stem component 10. Though not required, the lockingmechanism can be at an interface between the mounting portion 14 and theinner core 20. As shown in this figure, a pair of the stem protuberances16 a, 16 b can pass over a pair of the inner core protuberances 24 a, 24b, as the inner core protuberances 24 a, 24 b are configured tocompress. Once the stem protuberances 16 a, 16 b completely pass overthe inner core protuberances 24 a, 24 b, the stem protuberances can lockinto a pair of inner core concavities 25 a, 25 b, respectively. Theinner core concavities 25 a, 25 b are configured in dimension toinversely match the stem protuberances 16 a, 16 b such that a lockingaction occurs. Thus, an abutment of the protuberances occurs and canprevent unwanted motion between the head component and the stemcomponent after the prosthesis is inserted. The protuberances also serveto prevent the head component from slipping off the stem componentwithout intentional force, e.g., during removal by a surgeon. With thisand other similar designs, the stem component can be placed in a canalof the radius bone, followed by the fitting of the head component.

FIG. 10 shows the stem component, the inner core 20 and the outer shellbody 32 in a completed assembly configuration. As can be seen, thecylindrical inner core 20 component fits centrally within the outershell body 32. Thus, when the mounting portion 14 of the stem component10 is inserted fully within the core and shell, all three componentswill be configured coaxially. Though the outer shell body 32 and theinner core 20 are shown as two separate components, in practice, theouter shell body 32 and the inner core 20 can be assembled andsterilized prior to attachment to the mounting portion 14 of the stemcomponent 10. Thus, the surgeon would only be required to slide theassembled head component onto the stem component 10 by lining up theopen channels 26, 36 with the mounting portion 14, and sliding theradial head component 30 into place. In FIGS. 11-13, additional views ofan assembled prosthesis are shown.

When assembling the head component onto the mounting portion 14, due toelastic deformation of the inner core protuberances 24 a, 24 b, all ofthe protuberances 16 a, 16 b, 24 a, 24 b can be slid past opposingprotuberances under sufficient translational force. In this embodiment,the protuberances are shaped such that the force required to press theprotuberances past their opposing protuberances is intentional andreasonable, but not excessive.

FIG. 14 is a posterior oblique view of the human elbow depicting theradial head prosthesis in position within the proximal radius bone 38and articulating with the capitellum 39 of the distal humerus. As can beseen, the anchoring portion 12 is within the medullary canal of theproximal radius 38, and the radial head 30 is articulating with thecapitellum 39 of the distal humerus.

In FIGS. 15 and 16, a tool 40 is shown that can be used with theprosthesis of the present disclosure is shown. In FIG. 15, the tool 40is positioned in a first orientation with respect to proximal radius 38for inserting the radial head component 30 onto the mounting portion 14.In FIG. 15, the tool 40 is positioned in a second orientation withrespect to the proximal radius 38 for removing the radial head component30 from the mounting portion.

Specifically, with respect to FIG. 15, a first arm 42 and a second arm44 are shown that enable a surgeon to create translational force 45 tobe placed on the radial head component 30. The first arm 42 and thesecond arm 44 are tracked parallel to one another by a track 46 and aslider 48. The second arm 44 is connected to a handle 52 by a hinge 50.The handle 52 is designed such that by applying a squeezing force 51,translational force 45 is applied to the head component 30. Thus, inthis embodiment, the translational force mechanism is a lever. At theend of the first arm 42 is a pulling member 54 that acts to stabilizethe proximal radius 38 (or alternatively, the mounting portion 14). Atthe end of the second arm 44 is a pushing member 56 for pushing theradial head component 30 onto the mounting portion 14.

In FIG. 16, the same tool 40 as described in FIG. 15 can be used byflipping it upside down. Thus, the first arm 42 now acts to provide thetranslational force 45 and the second arm 44 stabilizes the proximalradius 38 (or alternatively, the mounting portion 14). Thus, the armsare characterized as the first arm 42 and the second arm 44 forconvenience only. It would be apparent to one skilled in the art thatthe first arm or the second arm can function as the stabilizer.Likewise, the first arm or the second arm can act to provide desiredtranslational force.

The use of such a tool is particularly helpful when a locking mechanismsuch as that described in FIGS. 1-13 is in place. Locking and unlockingcan be carried out as previously described. Specifically, in the presentembodiment, the tool can press the components onto one another whilemaintaining alignment of the dovetail shaped mount and groove. In theabsence of intentional and sufficient pressure to translate the headcomponent off of the stem component, the rigidity provided by thepolyethylene is sufficient to secure the modular components to eachother. Removal is accomplished by generating sufficient translationalpressure on the head component with the use of a specially designedhandle. This tool binds the far end of the head component whilestabilizing the proximal radius bone, and thereby the stem component.Translational force is generated which presses the protuberances of theinner core past the protuberances of the mounting portion, therebyreleasing the head component from the stem component.

A procedure that can be followed for the insertion of the modular radialhead prosthesis is as follows. If necessary, after resection of asubstantially unreconstructable radial head bone, a proximal edge of theradius bone can be removed by transverse sawing or some other removaltechnique. After the damaged radial head has been removed, the medullarycanal of the bone can then be broached with one or more of a series ofbroaches, the shapes of which approximate the various stem sizesavailable. Once an appropriate size stem component size has beenselected, the anchoring portion can be inserted into the proximal radiusbone such that the mounting portion protrudes from the proximal radiusbone. The head component can then be selected based upon parameters suchas proper ligament tensioning, circumference, and height. If desired,this assessment can be assisted with the use of plastic trials madeavailable for this purpose. After an appropriately sized head componentis selected, the forearm can be rotated so that the mounting portion ispositioned to receive the head portion, i.e., an assembled outershell/inner core combination or a single piece head component. If thehead component comprises an outer shell and an inner core, the headcomponent can either be assembled at the time of manufacture or by thesurgeon. In any event, the outer shell groove and the inner core grooveshould be positioned such that the grooves line up for accepting themounting portion. Once the stem component is in place and the properhead component is assembled and selected, the head component is thentranslated onto the stem component fully. If a locking mechanism is usedsuch as that described in FIGS. 1-13, a click will be palpable as thestem protuberances and the inner core protuberances slip fully past eachother. The prosthesis will then be secure within the canal of theproximal radius bone and is positioned to articulate with the capitellumof the distal humerus.

With the above figures and surgical procedures in mind, a modularprosthesis system for replacement of the radial head portion of theradius bone is disclosed comprising a stem component and a headcomponent. The stem component comprises an anchoring portion and amounting portion, and the head component can have an open channelconfigured to connect to the mounting portion along an assembly axisthat is transverse to a longitudinal axis of the stem component. Theconnection can be by a sliding motion. Though the system requires onlythat the assembly axis be transverse to the longitudinal axis of thestem component, for practical purposes, the transverse angle willgenerally be from about 45° to 135° with respect to the longitudinalaxis. This is due to the fact that as you approach angles closer toparallel with the longitudinal axis, the head component becomes moredifficult to put in place. In many incidences, the assembly axis willintersect the longitudinal axis at essentially a perpendicular angle.

The system can further comprise a locking mechanism to prevent the openchannel of the head component from indeliberately sliding on themounting portion once connected to the mounting portion. This isdesirable because once the prosthesis has become part of the functioningelbow joint, any slippage could require surgery for repair. Thus, theonly circumstance wherein sliding should be allowed should occur at thehand of the surgeon, with deliberate action. The locking mechanism canbe configured such as that shown in FIGS. 1-13, or by any other lockingmechanism known by those skilled in the mechanical arts. For example,after sliding the head component onto the mounting portion, the headcomponent can be locked in place with a pin or screw.

In one embodiment, the mounting portion can be configured for allowingthe head component to slide along a single axis via the open channel.Such an embodiment is shown in FIGS. 1-13 where the dovetail-shapedmounting portion is inversely matched with a dovetailed-shaped groove.Thus, the head component can be slid onto the mounting portion along asingle axis only.

Though not required, the head component can be inserted and removed fromthe mounting portion with a specially designed tool. Thus, the system ofthe present disclosure can further comprise a tool for inserting andremoving the head component while the stem component is in place withina radial canal. Such a tool can comprise a first arm for inserting thehead component onto the mounting portion or removing the head componentfrom the mounting portion; a second arm for stabilizing the radius bone;and a translational force mechanism for moving the first arm while thesecond arm stabilizes the radius bone. The terms “translation” and“stabilizing” are used loosely depending on whether the tool is beingused for insertion or removal of the head component, the arm acting toprovide the translational force and the arm acting to providestabilization can be changed. Thus, the terms are relative as to theaction, rather than to the specific structure. For example, wheninsertion of the head component is being carried out, the first armcarrying out the translational insertion does so by a pushing force, andthe second arm stabilizes the radius bone by a pulling force.Conversely, when removal of the head component is being carried out, thefirst arm removes the head component by a pulling force (i.e., the toolis flipped over, and the second arm stabilizes the radius bone by apushing force).

As part of the system, a method for fitting a damaged radius bone with amodular radial head prosthesis is disclosed comprising the steps ofsecuring a stem component partially within a proximal intramedullarycanal of the damaged radius bone such that a mounting portion of stemcomponent is exposed above the damaged radius bone; selecting a headcomponent that will provide a desired result; and sliding the headcomponent onto the mounting portion in a direction along an assemblyaxis that is transverse to a longitudinal axis of the stem component.Typically, a preliminary step of removing a radial head of the damagedradius bone is carried out prior to fitting the radius bone with theprosthesis of the present disclosure, though there can be circumstanceswhere this preliminary step is not necessary. Additionally, beforesecuring the stem component within the intramedullary canal, it may bedesirable to carry out the preliminary step of sizing the stem componentto securely fit within the proximal canal. This can be done using a setof broaches designed for this purpose. The stem component can be securedwithin the intramedullary canal by one of a number of techniquesincluding the use of cement, firm pressure into the canal, or impactingthe stem component into the canal, for example.

Once the stem component is in place, the next step of selecting anappropriate head component is carried out. Considerations can includeassessing a desired tensioning of one or more ligaments attached to theradius bone and/or assessing the height and shape of the head componentto be used. Aid in this area can be provided by the use of trialsdesigned for this purpose. Such trials can be plastic structuresconfigured to approximate the size and shape of the head component to beultimately placed on the mounting portion. It is appreciated that thetrials can be made of other suitable materials.

Referring to FIGS. 17 through 20, the inner core 20 and the outer shellbody 32 of the radial head component 30 are shown. In the variousembodiments, the outer shell body 32 can be comprised of ultra highmolecular weight polyethylene (UHMWPE). The outer shell body 32 can alsobe comprised of a suitable metal material such as cobalt chrome,titanium, or other biocompatible material. The inner core 20 can also bemade of a material that is identical to the radial head component 30(FIG. 19B) or as above described made of a softer material (FIG. 19A)that can otherwise be compressed when inserted over the stemprotuberances 16 a, 16 b or any other biocompatible material, as abovedetailed and as shown in FIG. 1.

In other embodiments, the inner core 20 and the outer shell body 32 arecomprised of the same material (FIG. 19B), for example, a metal such ascobalt chrome or titanium. By way of example, a mechanical fastener 60can be used to secure the outer shell body 32 to the inner core 20 inlieu of the compressible inner core protuberances 24 a, 24 b (FIG. 4).In addition, the head component 30 can be made of single piece ofbiocompatible material (FIG. 19C), such that the head component is aunitary construction. It is appreciated that a plurality of thefasteners 60 can be used to secure the outer shell body 32 to the innercore 20. Moreover, other types of exemplary connections may be used suchas chemical bonding, shrink fit and taper junctions. Furthermore, theouter shell body 32 can be configured to snap fit onto the inner core20, while another method can include mechanical threading on the innercore 20 with complementary mechanical threading on the outer shell body32. The outer body shell 32 of the radial head component 30 can also beconfigured to completely envelope the inner core 20, as shown in FIGS.17 and 18, or otherwise be positioned over the inner core 20 as to notcover the open channel 26 thus exposing varying lengths of the innercore 20, as shown in FIGS. 19A, 19B and 20.

With reference to FIGS. 21A through 24, a collar component 62 can beused to connect the radial head component 30 to the stem component 10.The collar component 62 can have a collar open channel 64 and a collarmounting location 66, which are complementary to the head open channel36 and the stem mounting location 14, respectively. The collar component62 can be configured to vertically align the radial head component 30and the stem component 10, as shown in FIG. 22. An angled collarcomponent 68 can also be configured to provide a pre-determined anglebetween the radial head component 30 and the stem component 10, as shownin FIG. 25. As such, the angled collar component 68 can be configured atvarious angles, for example, between vertical (i.e., 180°) and narrowerangles to match the native geometry of the bones, as shown in FIG. 14.It can be appreciated that the radial head component 30 and the stemcomponent 10 can attach to the collar component 62 or the angled collarcomponent 68 regardless of its length or angle.

In the various embodiments, the radial head component 30 can have aunitary construction (i.e., one-piece), thus omitting the inner core 20and outer shell body 32. In this arrangement, the radial head component30 can be constructed of metal such as cobalt chrome, titanium or anyother suitable biocompatible material for implementation into the humanbody. By way of example, the radial head component 30 can be secured toeither the stem mounting portion 14 or the collar mounting portion 66 ofthe collar component 62 with a suitable mechanical fastener 60.

With reference to FIGS. 21A and 21B, the head component 30 includes afirst connection portion 70 that connects to a second connection portion72 on the collar component 62. The collar component 62 also includes athird connection portion 74 that connects to a fourth connection portion76 on the stem component 10. It can be appreciated that the secondconnection portion 72 can be distal from the third connection portion 74and can be on opposite ends of the collar component 62. As shown in FIG.21A, the first connection portion 70 can be the open channel 26 on thehead component 30. The second connection portion can be the collarmounting portion 66. The third connection portion 74 can be the collaropen channel 64. The fourth connection portion 76 can be the mountingportion 14 on the stem component 10. As shown in FIG. 21B, the firstconnection portion 70 can be a head component mounting portion 78. Thesecond connection portion can be the collar open channel 64. The thirdconnection portion 74 can be the collar mounting portion 66. The fourthconnection portion 76 can be a stem component open channel 80.

It can be appreciated that the various components of the modularprosthesis system can use various connection portions with myriadconfigurations. By way of example, the mounting portion on the variouscomponents is configured in a T-shaped protrusion generally indicated byreference numeral 82. A complementary open channel 84 is similarlyconfigured in a T-shape to accept the T-shaped protrusion 82. Withreference to FIG. 23, it can be appreciated that other configurationsare suitable such as, but not limited to, a cylindrical configuration86, a dove-tail configuration 88, and a star shaped configuration 90. Itcan also be appreciated that, regardless of the configuration, variousfits can be used such as, but not limited to, an interference fit, ataper lock fit and a sliding fit secured by a mechanical fastener 60. Itcan further be appreciated that the mechanical fastener 60 can beinserted through an aperture and contact the T-shaped protrusion. Themechanical fastener can also connect to the T-shaped protrusion suchthat the fastener 60 can be inserted through a fastener aperture 92 inthe open channel and/or in the mounting location. It can be additionallyappreciated that the fastener can be placed at various angles andpositioned to further secure the components of the prosthesis.

It can be appreciated that the various components of the modularprosthesis can be scaled to fit the patients native bone structure. Acollar length 94 (FIG. 22) and a collar angle 96 (FIG. 24) can bevariable among multiple collar components 62, 68, while the collarmounting location 66 and the collar open channel 64 can have a fixeddimension to facilitate interchangeability among other stem components10 and head components 30. With reference to FIG. 20, it can also beappreciated that an inner core length 98 can vary such that the innercore body 22 can be completely contained within the head component innerhollow 34 or extend beyond an outer body shell aperture 100. It isfurther appreciated, that various dimensions such as length, diameter,thickness etc. can be varied to more closely match the native bonestructure of the patient, as shown in FIG. 14.

With reference to FIGS. 26A-26D, a threaded post 102 and a complementarythreaded aperture 104 can be used to connect the collar component 62 tothe head component 30 and the stem component 10. With reference to FIG.26A, the first connection portion 70 of the head component 30 caninclude the threaded aperture 104. The second connection portion 72 ofthe collar component 62 can include the threaded post 102 that canengage with and connect to the complementary threaded aperture 104 onthe head component 30. The third connection portion 74 of the collarcomponent 62 can include the above described T-shaped protrusion 82. Thefourth connection portion 76 of the stem component 10 can include theabove described T-shaped channel 84, which can connect with the T-shapedprotrusion 82 included on the third connection portion 74 of the collarcomponent 62. It can be appreciated that the angled collar component 68(FIG. 26D) can be similarly configured to the collar component 62 (FIGS.26A-26C) and, thus, can be used interchangeably.

With reference to FIG. 26B, the first connection portion 70 on the headcomponent 30 can include the T-shaped protrusion 82. The secondconnection portion 72 of the collar component 62 can include thecomplementary T-shaped channel 84 that can connect with and engage theT-shaped protrusion 82 included on the first connection portion 70 ofthe head component 30. The third connection portion 74 of the collarcomponent 62 can include the threaded post 102. The fourth connectionportion 76 of the stem component 10 can include the complementarythreaded aperture 104 that can engage to and connect with the threadedpost 102 included on the third connection portion 74 of the collarcomponent 62.

With reference to FIG. 26C, the first connection portion 70 of the headcomponent 30 can include the threaded aperture 104. The secondconnection portion 72 of the collar component 62 can include thethreaded post 102 which can engage with and connect to the threadedaperture 104 included on the first connection portion of the headcomponent 30. The third connection portion 74 of the collar component 62can also include the threaded post 102. The fourth connection portion 76on the stem component 10 can include the threaded aperture 104 that canengage with and connect to the threaded post 102 on the third connectionportion 74 of the collar component 62.

With reference to FIG. 26D, the first connection portion 70 of the headcomponent 30 can include the threaded aperture 104. The secondconnection portion 72 of the angled collar 68 can include the threadedpost 102, which can engage with and connect to the threaded aperture104. The third connection portion of the angled collar 68 can alsoinclude the threaded post 102. The fourth connection portion 76 of thestem component 10 can include the threaded aperture 104, which canengage with and connect to the threaded post 102. It can be appreciatedthat height 94 (FIG. 26C) and/or angle 96 of either the collar component62 or angled collar component 68 can be varied to accommodate the nativebone structure, as shown in FIG. 14. Moreover, the height 106 (FIG. 26C)of the threaded post 102 can be varied to further accommodate themodularity of the prosthesis. It can also be appreciated that the firstconnection portion 70, the second connection portion 72, the thirdconnection portion 74 and the fourth connection portion 76 can beconfigured in various ways including, but not limited to, the respectivethreaded posts 102 and threaded apertures 104 and various combinationsthereof.

With reference to FIG. 27, a kit 108 is shown including exemplary stemcomponents 10, collar components 62, angled collar components 68 andhead components 30. The kit 108 can include a collection of varioussizes and shapes of the above-mentioned components. For example, the kit108 can include a plurality of angled collar component 68 having varyingcollar angles 96. By way of further example, the kit 108 can include aplurality of head components 30 having varying shaped concave topportions 37 that complement the native bone to which they will contact.The kit 108 can also include a plurality of stem components 10 such thateach of the stem components 10 has varying size anchor portions 12 inthickness, taper design and/or length. Moreover, the kit 108 can includea plurality of collar components 62 having varying collar lengths 94 tofurther accommodate the native bone structure. It can be appreciatedthat the kit 108 can include numerous head components 30, angled collarcomponents 68, collar components 62, and stem components 10 of varioussizes, shapes and configurations so that the modular prosthesis systemcan be assembled to closely match the native bone structure.

The kit 108 provides the plurality of head components 30, angled collarcomponents 68, collar components 62, and stem components 10 that can beassembled and adjusted during a medical procedure to provide a fit thatcan be in-situ determined and adjusted. It can be appreciated that amedical professional can determine a proper length and angle and selectamong the components of the kit 108 to achieve the proper length andangle. Nevertheless, the medical professional can select and substitutecomponents in-situ to adjust to achieve the proper length and angle.

Turning now to FIGS. 28-34, a modular radial head prosthesis system isshown and generally identified at reference numeral 120. The modularradial head prosthesis system 120 can generally include an articulatingcomponent 122, a series of head components 124 a, 124 b and 124 c (FIG.31), a stem component 126 and a fastener 128. As will become appreciatedfrom the following discussion, the modular radial head prosthesis system120 can provide a series of head components 124 a, 124 b and 124 chaving different dimensions (such as height dimensions H₁, H₂ and H₃(FIG. 31) that can be selectively and alternatively coupled with thearticulating component 122, the stem component 126 and the fastener 128.The modular radial head prosthesis system 120 allows a surgeon to use aselected articulating component 122 and choose a desired head componentfrom the plurality or kit of head components according to a patient'sparticular needs. A common stem component 126 can also be used toselectively interconnect with any of the head components 124 a, 124 band 124 c. As can be appreciated, different head components havingdifferent geometries and/or dimensions may be preferred from one patientto the next. For example, in some cases it may be desired to build upthe height (see H₁, H₂ and H₃, FIG. 31) of the distal radius dependingupon the amount of host radius that is being replaced. The modularity ofthe modular radial head prosthesis system 120 can allow a surgeon tohave common articulating components 122, stem components 126 and/orfasteners 128 that can be intraoperatively coupled with various headcomponents 124 a, 124 b and 124 c to create an assembled modular radialhead prosthesis that provides the desired geometry and profile for anyparticular patient. It is also appreciated that while a singlearticulating component, stem component 126 and fastener 128 aredescribed and shown with respect to the drawings, additionalarticulating components 122, stem components 126 and fasteners 128 mayalso be provided that can offer various material characteristics and/orgeometric configurations as further discussed herein.

With particular attention now given to FIGS. 28-30, the articulatingcomponent 122 will be described in greater detail. The articulatingcomponent 122 can include a body portion 130 that is fashioned toapproximate the dimensions of a damaged or removed radial head. Thus,the outer shape is roughly cylindrical, having a slightly concaved topor articulation portion 132 for natural articulation with the capitellum(see reference 39, FIG. 14) or alternatively a capitellar implant.Because the articulating component 122 is the portion of the prosthesisthat will articulate with the capitellum 39 upon joint movement, thisstructure can be constructed of a biologically accepted rigid material.Such a material can include, for example, metal, alloy, PEEK, UHMWPE, orceramic. If the rigid material is metal or alloy, appropriate materialscan include for example, titanium, stainless steel, and cobalt chrome.The articulating component 122 can include a central extension portion136 and a radial lip 138. In one example, the central extension portion136 can generally define a cylindrical member that has an outer geometrythat substantially matches an outer profile of the articulatingcomponent 122, but has a reduced diameter. Depending from a distalsurface 140 of the central extension portion 136 are connection portions142. In the example shown, the connection portions 142 generally takethe form of male insertion portions or posts 144 having conical endportions 148 that extend from circumferential extension portions 150. Anarrowed neck 152 is formed generally between the distal surface 140 ofthe central extension portion 136 and the circumferential extensionportions 150.

The connection portions 142 can generally define longitudinal channels154 formed therethrough. As will be described herein, the channels 154can allow the connection portions 142 to compress radially inwardlyduring an assembly step. The connection portions 142 are monolithic andformed integral with the remaining structure of the articulatingcomponent 122. In other examples, the connection portions 142 can bemodular and be formed of distinct material from the remainder of thearticulation component 122. While a pair of connection portions 142 areshown and described with respect to the disclosed embodiments, it isappreciated that additional or fewer connection portions 142 may beprovided on the articulating component 122. In the particular exampleshown, a pair of connection portions 142 formed generally toward aperimeter of the distal surface 140 of the central extension portion 136can provide anti-rotation characteristics in an assembled position aswill become appreciated from the following discussion. The connectionportions 142 can additionally or alternatively be provided elsewhere onthe distal surface 140.

With reference now to FIGS. 28-31, the head component 124 a will bedescribed in greater detail. For discussion purposes, description of thehead component 124 a will be given, however, it is appreciated that thehead components 124 b and 124 c shown in FIG. 31 are constructedsimilarly, but have different dimensions. The head component 124 agenerally comprises a generally cylindrical body 160 that has agenerally bulbous proximal portion 162 and a cylindrical distal portion164. A countersink 168 is formed in a proximal end 170 of the bulbousproximal portion 162. The countersink 168 can generally terminate at aproximal surface 172 and is defined within a cylindrical wall 174. Aradial annular rim edge 176 is provided at the proximal end 170.

A pair of connection portions 180 are formed in the cylindrical body160. In general, the connection portions 180 include female receivingportions or closed bores 182 formed into the proximal surface 172. Eachof the female receiving portions 182 generally include an angled beveledentrance surface 184 and a reduced diameter portion 186. As can beappreciated, the connection portions 180 (FIGS. 32A-B) can be providedto interconnect with the connection portions 142 provided on thearticulating component 122 to form an intraoperative coupling mechanism185. In this way, a pair of female receiving portions 182 are formedgenerally toward a perimeter of the proximal surface 172 tocooperatively align for receipt of the male insertion portions 144 ofthe articulating component 122. It is appreciated, however, thatadditional or fewer connection portions 180 may be provided on thecylindrical body 160 of the head component 124 a as desired.Furthermore, while male insertion portions 144 have been described asassociated with the articulating component 122 and female receivingportions 182 have been described in relation to the head component 124a, these features may be provided on opposite components or mixed maleinsertion/female receiving portions.

The head component 124 a can further include another connection portionin the form of a T-shaped channel 190 having an entrance generallythrough a sidewall 192 of the cylindrical body 160. As best illustratedin FIG. 29, the T-shaped channel 190 can terminate at an endwall 193within the cylindrical body 160. Explained differently, the T-shapedchannel 190 does not extend completely through the diameter of the headcomponent 124 a. The T-shaped channel 190 includes opposed arcuatesidewalls 194 and an opposed undercut ledge 195. A counterbore 196 isalso formed into the sidewall 192 of the cylindrical body 160. Ingeneral, the counterbore 196 can be coaxial with a length defined by theT-shaped channel 190. As shown in FIG. 33, a reduced diameter portion orcollar 198 is provided in the cylindrical body 160 generally between thecounterbore 196 and the T-shaped channel 190. As shown in FIG. 29, theT-shaped channel 190 can extend through a distal end 200 while thecounterbore 196 is provided exclusively on the sidewall 192.

With specific reference now to FIG. 31, the head components 124 a, 124 band 124 c are shown having various heights measured between respectiveproximal and distal ends 170 and 200. In general, the connectionportions 180 are geometrically consistent between each of the headcomponents 124 a, 124 b and 124 c for selectively interconnecting withthe connection portions 142 of the articulating component 122. Again,while the height dimensions are shown having various dimensions betweenthe respective head components 124 a, 124 b and 124 c, other geometricalrelationships may be different between the respective head components124 a, 124 b and 124 c to allow a surgeon to selectively andintraoperatively choose a particular head component that is desired fora given patient's circumstances. The head components 124 a, 124 b and124 c can be formed from metal or alloy, such as, but not limited to,titanium, stainless steel and cobalt chrome.

The stem component 126 will now be briefly described. The stem component126 can generally include a stem connection portion in the form of aT-shaped protrusion 210 having a threaded blind bore 212. Again, whileone stem component 126 is described and shown in the drawings, it isappreciated that a plurality of stems may be provided (see kit 108, FIG.27).

An exemplary method of assembling the modular radial head prosthesissystem 120 will now be described according to one example. At theoutset, once a head component 124 a, 124 b or 124 c has been selectedthat accommodates the needs of a particular patient, the articulatingcomponent 122 can be selected having a particular material depending onthe needs of the particular patient, for example, for articulation witha natural bone or a capitellar implant. The articulation component 122can be attached to the proximal end 170 of the head component (such as124 a). A surgeon can generally align the male insertion portions 144 onthe central extension portion 136 of the articulating component 122 forreceipt into the complementary female receiving portions 182 provided onthe proximal surface 172 of the head component 124 a.

With particular reference now to FIGS. 32 a and 32 b, the male insertionportions 144 are advanced linearly along their axes into the femalereceiving portions 182. As the conical end portions 148 negotiate acrossthe angled entrance surfaces 184, they compress radially inwardly asthey are advanced through the reduced diameter portions 186 of thefemale receiving portions 182. Once the conical end portions 148 passbeyond the reduced diameter portions 186, the conical end portions 148retract outwardly to their normal static position. The male insertionportions 144 can snap-fit into the female receiving portions 182. Asshown in FIG. 32 b, the neck 152 of the male insertion portions 144 islocated in an aligned position with the reduced diameter portion 186while the circumferential extension portion 150 of the male insertionportion 144 is captured by the reduced diameter portion 186. Notably,the central extension portion 136 is configured for receipt into thecountersink 168 and the radial lip 138 of the articulating component 122is configured to rest on the radial edge 176 of the head component 124a.

As shown in FIGS. 34-35, the stem component 126 can be operably attachedto the head component 124 a by slidably advancing the T-shapedprotrusion 210 into the complementary shaped T-shaped channel 190 of thecylindrical body 160. The fastener 128 can be advanced into thecounterbore 196 formed in the sidewall 192, such that its shank extendsthrough the collar 198 of the cylindrical body 160 and threadably mateswith the threaded blind bore 212 of the stem component 126.

With reference now to FIGS. 36-38, a modular radial head prosthesissystem according to another example of the present teachings is shownand generally identified at reference numeral 220. The modular radialhead prosthesis system 220 can generally include an articulatingcomponent 222, a head component 224, a stem component 226 and a fastener228. As with the modular radial prosthesis system 120 described above,the modular radial head prosthesis system 220 can be provided in variouscomponents as a kit, and having different dimensions for selectedcomponents. In this way, the modular radial head prosthesis system 220can allow a surgeon to use a selected articulating component 222 andchoose a desired head component 224 from a plurality of head componentsand a stem component 226 from a plurality of stem components to satisfya given patient's particular needs. A series of head components 224having different dimensions, such as various height dimensions describedabove with respect to FIG. 31, can be provided. Similarly, various stemcomponents 226 having various height dimensions can be provided.

The articulating component 222 can include a body portion 230 that isfashioned to approximate the dimensions of a damaged or removed radialhead. Thus, the outer shape is roughly cylindrical, having a slightlyconcave articulating portion 232 (FIG. 37) for natural articulation withthe capitellum (see reference 39, FIG. 14), or implant. Because thearticulating component 222 is the portion of the prosthesis that willarticulate with the capitellum 39 upon joint movement, this structurecan be constructed of a biologically accepted rigid material. Such amaterial can include, for example, metal, alloy, PEEK, UHMPWE orceramic. The articulating component 222 can include an angled extensionportion 236 that can generally include a male tapered portion thatextends to a distal surface 240. Depending from the distal surface 240of the extension portion 236 is a connection portion 242. In the exampleshown, the connection portion 242 generally takes the form of acylindrical member 244 that extends from a location offset from a centerpoint of the distal surface 240. The cylindrical member 244 can have aT-shaped slot 248 formed therein. In the example shown, the T-shapedslot 248 can extend entirely through the cylindrical member 244. Theconnection portion 242 is monolithic and formed integrally with theremaining structure of the articulating component 222. Alternatively,the connection portion 242 can be modular and be formed of a distinctmaterial. Because the connection portion 242 is formed at a radiallyoffset location relative to a center point of the distal surface 240,the connection portion 242 can provide anti-rotation characteristics inan assembled position as will become appreciated from the followingdiscussion.

Additional description of the head component 224 will now be describedin greater detail. The head component 224 comprises a generallycylindrical body 260 that has a generally bulbous proximal portion 262and a cylindrical distal portion 266. A countersink 268 is formed on aproximal end 270 of the bulbous proximal portion 262. The countersink268 can generally include a female tapered wall that has a geometrycomplementary with the tapered surface of the extension portion 236 ofthe articulating component 222. The countersink 268 can generallyterminate at a proximal surface 272 for engagement with the distalsurface 248.

A connection portion 280 (FIG. 37) is formed in the cylindrical body260. In general, the connection portion 280 can include a femalereceiving portion 282 formed into the proximal surface 272. The femalereceiving portion 282 can generally include a geometry that is suitableto receive the cylindrical portion 244 of the connection portion 242 onthe articulating component 222. The connection portion 280 of the headcomponent 224 can facilitate alignment for interconnection with the stemcomponent 226 as will be described. The connection portions 242 and 280can collectively provide an articulation coupling mechanism 281 (FIG.37). In the example shown, the connection portion 242 of thearticulating component 222 is not configured to directly interconnectwith the connection portion 280 of the head component 224. Notably, theconnection portion 280 on the head component 224 is also offset from acenter point of the head component 224 a distance that is compatible foralignment and receipt of the cylindrical portion 244 of the connectionportion 242 of the articulating component 222.

The head component 224 can further include another connection portion inthe form of a T-shaped channel 290 having an entrance generally througha sidewall 292 of the cylindrical body 260. As illustrated in FIGS.36-38, the T-shaped channel 290 can terminate at an end wall 291 withinthe cylindrical body 260. Explained differently, the T-shaped channel290 does not extend completely through the diameter of the headcomponent 224. A counterbore 296 is also formed into the sidewall 292 ofthe cylindrical body 260 opposite the T-shaped channel 290. In general,the counterbore 296 can be coaxial with a length defined by the T-shapedchannel 290. As best illustrated in FIG. 37, a reduced diameter portionor collar 298 is provided in the cylindrical body 260 generally betweenthe counterbore 296 and the T-shaped channel 290. As illustrated in FIG.36, the T-shaped channel 290 can extend through a distal end 300 of thecylindrical body 260 while the counterbore 296 is provided exclusivelyon the sidewall 292.

With particular reference now to FIG. 36, the stem component 226 will bedescribed in greater detail. The stem component 226 can include alongitudinally extending body portion 304, a platform 306 and a stemconnection portion in the form of a T-shaped protrusion 308. A threadedblind bore 312 can be provided in the T-shaped protrusion 308 to alignwith the counterbore 296 for receipt of a fastener.

An exemplary method of assembling the modular radial head prosthesissystem 220 will now be described according to one example. At theoutset, a surgeon can select a given articulating component 222, a headcomponent 224 and a stem component 226 that provide the desireddimensions, materials, etc. according to a patient's particular needs.Next, the cylindrical member 244 of the connection portion 242 on thearticulating component 222 is advanced axially into the connectionportion 280 of the head component 224. Next, the T-shaped protrusion 308on the stem component 226 can be slidably advanced into the T-shapedchannel 290 of the head component 224. During the advancement of theT-shaped protrusion 308 on the stem component 226, the T-shapedprotrusion 308 will slidably interconnect with the T-shaped channel 290of the head component 224 as well as the T-shaped slot 248 on thearticulating component 222, thereby coupling the articulating component222, head component 224 and stem component 226 together. In other words,the T-shaped channel 290 and the T-shaped slot 248 are co-alignedchannels for receipt of the T-shaped protrusion 308 to simultaneouslycouple the head 224, the stem 226, and the articulation portion 222. Thefastener 228 can then be advanced into the counterbore 296 formed in thesidewall 292, such that its shank extends through the collar 298 of thecylindrical body 260 and threadably mates with the threaded blind bore312 on the stem component 226.

Turning now to FIGS. 39-42, a modular radial head prosthesis systemaccording to additional features is shown and generally identified atreference numeral 320. The modular radial head prosthesis system 320 cangenerally include an articulating component 322 and a head component324. As will be described, the articulating component 322 can be formedof a polymeric material and be reduced in size during an assembly step,such as by placing it in a freezer or exposing it to liquid nitrogen.The articulating component 322 can then be coupled to the head component324 by locating a first connection portion 326 of the articulatingcomponent 322 relative to a second connection portion 328 of the headcomponent 324 and allowing the articulating component 322 to return toambient temperature causing the first connection portion 326 tointerlock with the second connection portion 328. The first connectionportion 326 can be a male extension member and the second connectionportion 328 can be an undercut annular groove.

In one example, the head component 324 can further include an integrallyformed stem portion 330 extending therefrom. In other examples, amodular stem can be provided that mates with the head component 324.According to the present disclosure, the modular radial head prosthesissystem 320 can provide a series of head components 324 having differentdimensions, such as height dimensions described above with respect toFIG. 31 that can be selectively and alternatively coupled with thearticulating component 322. The modular radial head prosthesis system320 can allow a surgeon to use a selected articulating component 322 andchoose a desired head component 324 from a plurality or kit of headcomponents according to a patient's particular needs. As can beappreciated, different head components having different geometriesand/or dimensions may be preferred from one patient to the next. As withthe other embodiments disclosed herein, in some cases, it may be desiredto build up the height of the distal radius depending upon the amount ofhost radius that is being replaced.

The modularity of the modular radial head prosthesis system 320 canallow a surgeon to have a common articulating component 322 that can beintraoperatively coupled with various head components 320 to create anassembled modular radial head prosthesis that provides the desiredgeometry and profile for any particular patient. It is also appreciatedthat while a single articulating component and head component aredescribed and shown with respect to the drawings, additionalarticulating components 322 may also be provided that can offer variousmaterial characteristics and/or geometric configurations as describedherein.

The articulating component 322 will now be described in greater detail.The articulating component 322 can include a body portion 330 that isconstructed to approximate the dimensions of a damaged or removed radialhead. Thus, the outer shape is roughly cylindrical, having a slightlyconcaved top or articulating portion 332 for natural articulation withthe capitellum (see reference 39, FIG. 14) or alternatively a capitellarimplant. Because the articulating component 322 is the portion of theprosthesis that will articulate with the capitellum 39 upon jointmovement, this structure can be constructed of a biologically acceptedrigid material. As identified above, such a material can include, forexample, a polymeric material (UHMWPE) but may also include othermaterials that are suitable for articulation and can provide a reductionin size that allows for assembly of the first and second connectionportions 326 and 328 described above.

The articulating component 322 can include the first connection portion326 that can be in the form of an annular undercut 334. The undercut 334can have an upper ridge 336 a lower ridge 338 and a lip 339. Anextension portion 340 can be formed on one side of the articulatingcomponent 322. The extension portion 340 can generally include acylindrical member that has an outer geometry that substantially matchesan outer profile of a cavity 344 defined on the head component 324, buthas a reduced diameter. The extension portion 340 can be located offsetfrom a centerpoint of the articulating component 322 to inhibit rotationof the articulating component 322 relative to the head component 324 inan assembled position. In another configuration, the articulatingcomponent 322 can be keyed to the head component 324.

The head component 324 can generally comprise a cylindrical body 350that has a central recess 352. The second connection portion 328 cancollectively include an annular groove 354 and an upper ridge 356 formedaround the head component 324. The head component 324 can be formed of ametal or metal alloy, such as, but not limited to, titanium, stainlesssteel and cobalt chrome. It is appreciated that while the firstconnection portion 326 has been shown and described as part of thearticulation component 322 and the second connection portion 328 hasbeen shown and described as part of the head component, the location ofthese features may be reversed. Furthermore, it is contemplated thatother geometries may be alternatively be provided that attain acompression fit between the articulating component 322 and the headcomponent 324.

An exemplary method of assembling the modular radial head prosthesissystem 320 will now be described according to one example. At theoutset, once a head component 324 has been selected that accommodatesthe particular needs of a given patient the articulating component 322can also be selected. As further discussed herein, selection of thearticulating component 322 and the head component 324 can be based, atleast in part, on first determining a distance between a proximal radiusand a humerus of the patient. The articulating component 322 can then beshrunk in size. In one example, the articulating component 322 can beexposed to a reduction in temperature, such as by placing it in afreezer or subjecting it to liquid nitrogen. As can be appreciated, bycooling the components, it contracts or shrinks and the reduction insize can allow the outer diameter of the lip 339 to be less than aninner diameter of the ridge 356 on the head component 324. In thisregard, the lip 339 of the articulating component can be advanced intothe recess 352 of the head component 324. Concurrently, a user can alignthe extension portion 340 of the articulating component 322 with receiptinto the cavity 344 of the head component 324. The upper ridge 336 ofthe first connection portion 326 can rest on top of the ridge 356 of thesecond connection portion 328. The articulating component 322 is thenallowed to return to ambient temperature (FIG. 42). Returning to ambienttemperature, or more specifically body temperature when implanted,allows the lip 339 of the undercut portion 334 to expand and be capturedwithin the groove 354 of the head component 324 as illustrated in FIG.42. This can result in a compression fit between the articulatingcomponent 322 and the head component 324. According to other examples,the head component 324 can additionally or alternatively be subjected toan elevated temperature that causes the inner diameter of the ridge toexpand.

The description of the disclosure is merely exemplary in nature and,thus, variations that do not depart from the gist of the disclosure areintended to be within the scope of the disclosure. Such variations arenot to be regarded as a departure from the spirit and scope of thedisclosure. It is to be understood that the above-described arrangementsare only illustrative of the application of the principles of thepresent disclosure. Numerous modifications and alternative arrangementsmay be devised by those skilled in the art without departing from thespirit and scope of the present disclosure and the appended claims areintended to cover such modifications and arrangements. Thus, while thepresent disclosure has been shown in the drawings and fully describedabove with particularity and detail in connection with what is presentlydeemed to be the most practical and preferred embodiment(s) of thedisclosure, it will be apparent to those of ordinary skill in the artthat numerous modifications, including, but not limited to, variationsin size, materials, shape, form, function and manner of operation,assembly and use may be made, without departing from the principles andconcepts of the disclosure as set forth in the claims.

1. A method for implanting a prosthesis system for replacement of a headportion of a proximal radius, comprising: determining a distance betweena proximal radius and a humerus; selecting one of a first head componentor a second head component based on the determination, the first andsecond head components having unique heights; connecting the selectedfirst or second head component to an articulation component; andconnecting a stem component to the selected first or second headcomponent.
 2. The method of claim 1 wherein connecting the selected headcomponent comprises: inserting a male insertion member formed on one ofthe articulation component and the selected head component into a femalereceiving member formed on the other of the articulation component andthe selected head component.
 3. The method of claim 1 wherein connectingthe stem component to the selected head component comprises: slidablyadvancing a T-shaped protrusion formed on one of the selected headcomponent and the stem component into a complementary shaped female slotformed on the other of the selected head component and the stemcomponent.
 4. A method for implanting a prosthesis system forreplacement of a head portion of a proximal radius, comprising:determining a distance between a proximal radius and a humerus;selecting an articulation component based on the determination, thearticulation component having a first connection portion; selecting ahead component based on the determination, the head component having asecond connection portion; reducing a dimension of one of thearticulation component or the head component from a first size to asecond size; advancing one of the articulation component or the headcomponent into contact with the other of the articulation component orhead component; and returning the dimension to the first size such thatthe first and second connection portions interlock.
 5. The method ofclaim 4 wherein reducing a dimension comprises: cooling one of thearticulation component or the head component such that an outer diameterof a lip on one of the articulation component or the head component isreduced.
 6. The method of claim 5 wherein advancing comprises: passingthe lip into a recess formed on the other of the articulation componentor the head component.
 7. The method of claim 6 wherein returning thedimension to the first size comprises: expanding the lip into anundercut formed on the other of the articulation component or the headcomponent, the undercut having a ridge that captures the lip.
 8. Themethod of claim 4 wherein advancing comprises: inserting an extensionportion on one of the articulation component or the head component intoa cavity defined on the other of the articulation component and the headcomponent, the extension portion and the cavity being positioned at alocation that is offset from a central axis of the prosthesis system. 9.The method of claim 1 wherein connecting the selected head componentcomprises: slidably advancing a T-shaped protrusion formed on the stemcomponent into a complementary shaped female slot formed on thearticulation component.
 10. The method of claim 1 wherein connecting theselected head component comprises: resting a radially extending lipformed on the articulation component on a radially extending edge formedon the selected head component.
 11. The method of claim 1 whereinconnecting the stem component comprises: extending a fastener into thestem component and into the selected head component.
 12. The method ofclaim 2 wherein connecting the stem component comprises: slidablyadvancing a T-shaped protrusion formed on the stem component into acomplementary shaped female slot formed on the male insertion member.13. The method of claim 12 wherein connecting the head componentcomprises: aligning the complementary shaped female slot with anothercomplementary shaped female slot formed on the head component.
 14. Themethod of claim 2 wherein inserting the male insertion member into thefemale receiving member comprises: compressing a portion of the maleinsertion member radially inwardly.
 15. The method of claim 2 whereininserting the male insertion member into the female receiving membercomprises: capturing a circumferential extension portion formed on themale insertion component with a reduced diameter portion formed in thefemale receiving member.
 16. The method of claim 3 wherein connectingthe stem component comprises: extending a fastener into the T-shapedprotrusion and into the selected head component.
 17. The method of claim16 wherein extending the fastener into the T-shaped protrusioncomprises: threadably engaging the fastener with the T-shapedprotrusion.
 18. A method for implanting a prosthesis system forreplacement of a head portion of a proximal radius, comprising:determining a distance between a proximal radius and a humerus;selecting an articulation component based on the determination, thearticulation component having a first connection portion; selecting ahead component based on the determination, the head component having asecond connection portion; increasing a dimension of one of thearticulation component or the head component from a first size to asecond size; advancing one of the articulation component or the headcomponent into contact with the other of the articulation component orhead component; and returning the dimension to the first size such thatthe first and second connection portions interlock.
 19. The method ofclaim 18 wherein increasing the dimension comprises: heating one of thearticulation component or the head component such that an inner diameterof a ridge on one of the articulation component or the head component isincreased.
 20. The method of claim 19 wherein advancing comprises:passing the ridge into a recess formed on the other of the articulationcomponent or the head component.